When this transmitter operates at a lower frequency, say
1746 kc, the standard aircraft radio compass can be used to
find the direction to the transmitter. No suitable standard
equipment for ground direction-finding has been available to
the project.
c. Receivers and Recorders Used
For the T-49 and T-69 radiosonde transmitters, standard ground-
station equipment was used to receive and record the signal. An
appropriate receiver (National 110 for the T-49 and SCR-658 for the
T-69) feeds the sigpal through a frequency meter and into a Friez
recorder, model AN}Fl~Q-1(). With this system, frequencies between
10 and 200 cycles per second can be recorded.
When the Olland-Cycle pressure moduletor is used, (see Section VI,
A,3) with low-frequency pulses indicating the completion of the pres-
sure or reference circuit, a recorder made by the Brush Development
Co. (Model BL 212) replaces the Friez recorder and frequency meter.
With the AM-1 transmitter, the usual ground receiver has been the
Hammarlund Super-Pro l.:odel SP-400-X. For aircraft operation, an
aircraft radio compass such as AH/.AJall -Y is used.
D. Batteries Used
To extend the life of the batteries used with the T-49 and T-69
transmitters, experimental packs were developed using both dry
and wet cells. A typical ''12-hour" dry-cell pack for the T-69
was composed of:
B supply: 135V--l ea. B90FL (especially assembled for N.Y.U.
by Burgess Battery Co.) or 6 ea. Burgess
XX30 in series--parallel
A supply: 6V--l ea. Burgess 2F4 or 2 ea. F4H in parallel
C bias supPLy: 45V tap of B90FL or XX30 assembly
With an AM-1 transmitter, the input power required is as follows:
"B" supply, 270 volts at about 300 milliamperes; rr~in "A" supply,
li volts at 600 milliemperes; and a separate "A" supply for the
power amplifier, ll volts at 200 millia.mperes. The battery pack
includes 8 Burgess XX45 or Eveready 467 in series--parallela
2 Burgess 4FH batteries in parallel; and one 4FH, respectively.
This pack lasts about 20 hours in fli~ht. Also included in the
battery container were batteries for auxiliary functions such as
Olland-Cycle or program-switch motors, ballast-control relays,
and bring-down mechanisms.
The problem of operating at cold temperature ~~s given much consid-
eration. Special cold temperature batteries were tried with in-
sufficient difference in performance to justify the added expense
and difficulty of procurement. In addition, it was felt that
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